Thermostatic device



July 31, 1928.

J. L. BROWN THERMOSTATIC DEVICE Filed July 14, 1925 Patented July 31, 1928.

PATENT OFFICE.

JOHN L. BROWN, OF CATONSVILLE, MARYLAND.

THERMOSTATIC DEVICE.

Application filed July 14, 1925. Serial No. 43,587.

efiicient of resistance, the said member being adapted to be located at or near the place or body whose temperature it is desired to detect or regulate. This member is substantially non-conductive at ordinary room temperatures, but upon attaining a predetermined elevated temperature it permits a suilicient flow of current to operate the electro-magnet, which thereupon may perform any desired function, such as giving a vlsual or audible alarm, or operating a cutaout switch or a valve.

A particular application of the invention is to electrically heated implements, such as sad irons and the like, and when associated with implements of this character it affords a positive and certain means of preventlng overheating of the iron or the like. Due to the simplicity of the device and the absence of moving parts in the thermostat per se, the device is of especial utility in electrically heated implements which are generally sub-. ject to a great deal of handling, as there is nothing in the device to get out of order and no adjustments are ,called for after the device has been assembled with the implement.

The sad iron which is described in this specification, by way of example, is illustrated in the accompanying drawings in which:

Figure 1 is a plan view of the iron partly broken away to showthe automatic cut-out mechanism;

Figure 2 is a section on line 2-2 of Figure 1' Figure 3 is a diagrammatic view of the various elements of the cut-out mechanism; and

Figure 4 is a diagrammatic view illus trating the general application of the device.

The. body-of the iron is indicated at 10 and the heating element, which may be of any well-known type, at 11. The exact construction of the iron and heating element is immaterial to the invention. The usual terminal posts are indicated at 12 and 13, these posts being adapted to receive the usual separable connector -leading to a suitable source of electric current. Post 13 is directly connected to one end of heating element 11 and post 12 is connected thereto by a conductor which includes switch S, hereinafter to be more fully described. Connecting terminals or posts 12 and 13, when switch S is closed, is a secondary circuit, in parallel with the heating circuit, including a glower element 14 and a solenoid 15. The glower element 14 is composed of a certain substance or combination of substances, pressed into the form of a tube or pencil, which renders it a non-conductor of electricity at the normal working temperatures of the iron but a conductor of electricity at relatively higher temperatures, as for instance, when the iron becomes overheated. It may be made of various materials and by varying its composition its conductivity point, that is the temperature at which it first serves to conduct an electrical current, may be varied at'will.

For example, a glower composed of 84% of zirconium oxide, 6% of yttrium oxide, 2% of titanium oxide and 8% of magnesium oxide will be quite satisfactory with certain types of irons. This material audits properties are well known in the art and one having knowledge thereof can readily select and use a composition which is suitable for the particular instrument with which it is to beused. Within the solenoid 15 is a core or armature 16 which I designate the switch control member, sinceit is adapted to cooperate with the vertically movable switch -member or plunger 17, of switch S, and to hold this member against the lower contact .18 against the action of spring 19, which normally urges switch member 17 upwardly.

For the purpose of holding plunger 17 in its lowermost position the switch control member 16is provided with a bevel or wedge shaped outer end 20 adapted to enter a correspondingly formed recess 21 in member 17. A light spring 22 normally presses the control member 16 toward the switch member 17 and the action of this spring 22 is only overcome when the solenoid 15 is energized by an electric current which draws the core or control member within the same.

Contact 18 is supported by a spring 23 which acts to insure firm contact between members 17 and From Figure 3 it will be seen that contact 18 is electrically connected to post 13 through both solenoid and, heating coil and that switch member17 is electrically connected to post 12. Current cannot pass, therefore, through the heating element unless switch member 17 is depressed and contact is made between it and member 18. The upper end of member 17 is provided with a button 24: by means of which it may be conveniently operated. So long as member 17 is in its lowermost position and is locked by the control member 16 current will flow through the heating element. Upon the heating element or iron becoming excessively heated, however, current will begin to flow through the glower element l land hence through solenoid 15, the glower element being so positioned in the iron as to become sufficiently heated to conduct an electrical current when the iron itself tends to become overheated. When current flows through solenoid 15 the control element 16 is retracted, the plunger 17 is released and is drawn upwardly by spring 19. The current flow to the heating element is then interrupted and the iron will begin to cool off. After it has cooled sufiiciently the current may again be supplied upon the depression of the plunger 17.

Figure 4 is a diagrammatic view designed to indicate the application of thedevice generally to the detection of the abnormal rise in temperature of a heated body or place. In this view 25 designates any body, place or machine subject to an abnormal rise in temperature, and 15 designates a solenoid in an electric circuit, supplied with a source of energy, and in series with the thermostatic element 14. The plunger of solenoid 15 is shown connected to a lever 26, which lever is adapted to perform any desired function. It will be understood from the foregoing that when element 14 attains a predetermined temperature by reason of its 10- cation at or in the neighborhood of the heated element 25, current will flow through the circuit in suflicient strength to operate the plunger of solenoid 15 and rotate lever 26.

From the foregoing description the construction and mode of operation of the device will be apparent. The device is especially suitable for application to all types of electrical implements when such are in the course of fabrication or may be added as an attachment to many types of instruments on the market. Its details may be widely varied, as will be apparent to one skilled in the art, and that form of the invention which is illustrated in detail by the drawings and above described is only one of many which are included within the spirit and scope of the invention.

Having thus described the invention, what is claimed as'new and desired to be secured by Letters Patent is:

1. A device of the class described comprising an electric circuit including an element, solid in form which is substantially non-conductive at room temperatures and which is conductive at elevated temperatures, said element maintaining its solid form at all temperatures, a translating device and a source of electrical energy in said circuit, said translating device being constructed to respond to a flow of current corresponding to a predetermined elevated temperature of said element.

2. A device of the class described comprising an electric circuit including an element, solid in form which is substantially non-conductive at roomtemperatures and which is conductive at elevated temperatures, said element maintaining its solid form at all temperatures, an electro-magnet and a source of energy in said circuit, and mechanism operated by said magnet upon a predetermined flow of current in the circuit.

In testimony whereof I hereunto aflix my signature.

OHN L. BROWN. 

